1. Field of the Invention
This invention relates to a recording and/or reproducing apparatus for recording and/or reproducing information along a recording track of a disc-shaped optical recording medium, and to a recording and/or reproducing method for recording and/or reproducing information signals along the recording track responsive to a request from a host apparatus.
2. Description of Related Art
In the present embodiment, an optical recording medium is provided with a signal recording layer and is in a disc shape. A light beam is illuminated on this signal recording layer to record and/or reproduce information signals.
Among these optical recording mediums, there is a replay-only optical disc in which a pit string corresponding to information for recording is formed at the outset on a disc substrate, such as a CD (Compact Disc) or a CD-ROM (CD-Read Only memory). In such replay-only optical disc, the major surface on the disc substrate, on which the pit string is formed, has the function of the signal recording layer.
An optical disc used for a s-called compact disc recordable system and which permits post-writing only once, referred to below as CD-R, is also put to practical application. In the CD-R, a signal recording layer, on which to record the information signals, is formed by a material of an organic dye based material. On illuminating a light beam on the signal recording layer, the portion illuminated is changed in reflectance to effect the recording. The reflectance of the signal recording layer is detected to reproduce the recorded signals.
As an optical recording medium, a phase change type optical disc which utilizes phase changes of the signal recording layer which enables rewriting of the information signals by exploiting phase changes of the signal recording layer, such as the CD-RW (CD-Rewritable), has also been put to practical use.
As for the optical discs, such as CD, CD-ROM, CD-R or CD-RW, a variety of design parameters are standardized in accordance with the standard termed CD-format. This allows to reproduce the CD-R or CD-RW, enabling post-writing only once or rewriting of information signals, even on an apparatus designed to reproduce a replay-only disc, such as CD or CD-ROM.
Meanwhile, in the CD-ROM, i.e., among the above-described various optical discs, a first address (physical address) defined as the time domain information, and a second address (logical address) defined as consecutive binary numbers, are used as the address information indicating the positions of the information signals recorded on the disc.
The first address, having three time units of minute (M), seconds (S) and frames (F) as its values, is termed an MSF value. The first address is recorded in the CD-ROM in a Q-channel in a sub-code recorded in a recording track. The second address is specified from a host device, such as a personal computer connected to outside the optical disc device by a logical address value, or a so-called LBA (logical block address).
If, in accessing specified recording data on an optical disc, an accessing position is specified by the second address from the host device, the optical disc converts this second address into the first address to access the optical disc. Thus, in an optical disc device, it becomes necessary to effect the processing of frequently converting the second address to the first address or vice versa by way of reciprocal address conversion.
In the conventional optical disc device, the following artifice is used in converting the LBA value as the second address into the MSF value as the first address: That is, a remainder obtained on dividing the LBA value by 75 is used as the value of a frame (F) in the first address. On the other hand, a quotient obtained by this calculation is further divided by 60 to give a second remainder which is used as the second (S) in the first address. The above quotient is used as the minute (M) in the first address.
In the above-described optical disc device, at least two division operations are required in converting the second address to the first address such that a lot of time is needed in carrying out the conversion processing. If this conversion processing is carried out not by employing a command for division in a CPU but by employing a bit shift command or by an addition command, the computing processing is complex and time-consuming. The result is that, in the conventional optical disc device, the response time in reading or writing data on or from an optical disc tends to be worsened.
Moreover, in developing a semiconductor chip, such as a decoder or encoder including the above-mentioned address conversion processing, the multiplying and dividing circuitry needs a large number of gates, resulting in a larger circuit scale, a high cost and an increased circuit space to lower the cost and size of the entire optical disc device.
Moreover, in the field of recording and/or reproduction, the upper limit values of the aforementioned LBA and MSF values tend to be increased in keeping pace with the tendency towards high recording density and capacity of the optical disc. Although it may be envisaged to introduce higher order values to the first address to cope with the increasing capacity of the optical disc, at least three division and multiplication operations are needed in the aforementioned address conversion processing, thus further protracting the processing time.
It is therefore an object of the present invention to provide a recording and/or reproducing method and apparatus, according to which the time involved in converting the first address defined in terms of the time domain information to the second address defined in terms of consecutive binary numbers and vice versa may be shortened, such that, even in case the capacity of the optical recording medium is increased, the address conversion processing may be executed efficiently.
The recording and/or reproducing apparatus according to the present invention records and/or reproduces information signals along a recording track and includes rotational driving means, recording and/or reproducing means, address conversion means and memory means. The rotationally driving means rotationally drives the optical recording medium at a pre-set speed. The recording and/or reproducing means is movable along the radius of the optical recording medium to record and/or reproduce the information signals on or from the recording track of the optical recording medium. The address converting means converts the first address in the optical recording medium as defined with the time domain information into the second address as defined with consecutive hexadecimal numbers. The memory means holds a conversion table for conversion of the uppermost order value of the time domain information in the first address to the second address value and vice versa. The address converting means reciprocally converts the first and second addresses using the conversion table held in the memory means.
In the recording and/or reproducing apparatus according to the present invention, the address conversion by the address conversion means takes place using the conversion table held by the memory means. Since the address conversion means is able to perform rough conversion, using the conversion table for conversion between the uppermost order value of the time domain information in the first address value and the second address value, the conversion processing can be performed efficiently for shortening the processing time.
The recording and/or reproducing method according to the present invention includes an address converting step and a recording and/or reproducing step in recording and/or reproducing information signals along a recording track of a disc-shaped optical recording medium. At the address converting step, the first address defined with the time domain information and the second address defined with consecutive hexadecimal numbers are converted reciprocally. At the recording and/or reproducing step, the information signals are recorded and/or reproduced on or from the optical recording medium using the address as converted at the address converting step. The address conversion at the address conversion step takes place using the conversion table for conversion between the uppermost order value in the time domain information in the first address and the value of the second address.
Since the address conversion means is able to perform rough conversion, using the conversion table for conversion between the uppermost order value of the time domain information in the first address and the second address value, the conversion processing can be performed efficiently for shortening the processing time.
In the recording and/or reproducing apparatus according to the present invention, address conversion by the address conversion means takes place using the conversion table held by the memory means. Since the address conversion means is able to effect rough conversion using a conversion table for reciprocal conversion between the uppermost order value in the time domain information and the second address value, it is possible to achieve efficient conversion processing to realize a shorter processing time. The result is that the response time in reading out or writing data on or from an optical recording medium may be shorter to realize high speed recording and/or reproduction.
On the other hand, since the number of the division or multiplication circuits can be reduced in case the address conversion processing is performed using a hardware such as semiconductor chip, the number of gates can be reduced. Even if the optical recording medium is increased in recording capacity, the address conversion may be made roughly using the uppermost order value of the first address, so that address conversion can be achieved efficiently and speedily.
According to the recording and/or reproducing method according to the present invention, in which the address conversion means is able to perform rough conversion, using the conversion table for conversion between the uppermost order value of the time domain information in the first address and the second address value, the conversion processing can be performed efficiently, with the processing time being shorter. So, even if the optical recording medium is increased in recording capacity, address conversion may be made roughly using the uppermost order value of the first address, so that address conversion can be achieved efficiently and speedily.